1. Field of the Invention
The present invention relates to a method for manufacturing a sealed body by which a device is protected against the air. One embodiment of the disclosed invention relates to a method for manufacturing a glass sealed body and a method for manufacturing a light-emitting device provided with the glass sealed body.
Note that in this specification, the light-emitting device refers to a display device such as an organic EL display device or a light source (a lighting device) such as lighting or a sign (e.g., a traffic light or a warning light). Further, the device includes a light-emitting element.
2. Description of the Related Art
In recent years, light-emitting devices which have electroluminescence (hereinafter, referred to as EL) elements using EL as self-luminous light-emitting elements have been actively researched. The light-emitting devices are used for organic EL display devices, organic EL lighting devices, and the like. Such light-emitting devices are also called organic light-emitting diodes. The light-emitting devices provided with EL elements have features suitable for display of moving images, such as high response speed and low-voltage, low-power consumption driving, and thus they have attracting great attention as next-generation display devices such as new-generation mobile phones or personal digital assistants (PDA).
For a light-emitting device in which. EL elements are arranged in a matrix, a driving method such as passive (simple) matrix driving or active matrix driving can be used. However, when the pixel density is increased, the active matrix type where each pixel (or each dot) is provided with a switch is considered to be advantageous because it can be driven at a lower voltage.
An organic EL element which is one of EL elements has a structure typified by a stacked structure of a hole-transport layer, a light-emitting layer, and an electron-transport layer. Materials for these layers are roughly classified into low molecular (monomer) materials and high molecular (polymer) materials, and thin film formation of the low molecular materials is carried out by an evaporation method, for example.
A hole-transport layer, a light-emitting layer, an electron-transport layer, or the like are layers involved in light emission and are interposed between an anode and a cathode. The layers involved in light emission which have a stacked structure between the anode and the cathode are collectively referred to as an organic EL layer in this specification. As luminescence from an organic EL element, light emission (fluorescence) which is generated in returning from a singlet excited state to the ground state, and light emission (phosphorescence) which is generated in returning from a triplet excited state to the ground state are known.
Unlike a liquid crystal display device which needs a backlight, an organic EL display device having organic EL elements is a self-luminous device and thus it has excellent visibility due to its capability of easily realizing high contrast and its wide viewing angle. That is, the organic EL display device is more suitable for a display device for outdoor use than a liquid crystal display device. A variety of applications of the organic EL display device, such as a display device of a mobile phone or a digital camera, and the like, have been proposed.
Further, with the use of an organic EL element, a planar light-emitting device having a large area can be easily formed. This is a feature which is difficult to be obtained in point light sources typified by incandescent lamps and LEDs or line light sources typified by fluorescent lamps. In addition, the organic EL element is estimated to have higher emission efficiency than incandescent lamps or fluorescent lamps. Therefore, the light-emitting element has attracted attention as a preferable next-generation lighting device.
The organic EL element has a disadvantage that when an organic EL layer and electrodes between which the organic EL layer is interposed are exposed to moisture or oxygen, the performance might be rapidly lowered. In this regard, as a technique for preventing exposure of the organic EL layer or both the electrodes to the air, for example, conventional technique described in Patent Document 1 is known. In the technique described in Patent Document 1, paste-like powdered glass is scanned along an edge of a glass substrate while being discharged from a nozzle, whereby a partition whose shape is a closed curve is formed of the powdered glass. After that, baking is performed so that the powdered glass is fused to be a frit glass. Further, the partition is pressed against the other glass substrate, and the partition and the other glass substrate are welded together by laser welding; thus, a highly airtight glass sealed body is formed. By protecting an organic EL element by the glass sealed body, deterioration of the organic EL element can be suppressed. When part or all of the glass sealed body has a property of transmitting visible light rays, even when a light-emitting element is provided in the glass sealed body, light can be extracted to the outside.